Poly(vinyl butyral) (PVB) is commonly used in the manufacture of polymer sheets that can be used as interlayers in light-transmitting laminates such as safety glass or polymeric laminates. Safety glass often refers to a transparent laminate comprising a poly(vinyl butyral) sheet disposed between two sheets of glass. Safety glass often is used to provide a transparent barrier in architectural and automotive openings. Its main function is to absorb energy, such as that caused by a blow from an object, without allowing penetration through the opening or the dispersion of shards of glass, thus minimizing damage or injury to the objects or persons within an enclosed area. Safety glass also can be used to provide other beneficial effects, such as to attenuate acoustic noise, reduce UV and/or IR light transmission, and/or enhance the appearance and aesthetic appeal of window openings.
In many applications it is desirable to use safety glass that not only has the proper physical performance characteristics for the chosen application, but also has light transmission characteristics that are particularly suitable to the end use of the product. For example, it will often be desirable to limit infrared radiation transmission through laminated safety glass in order to provide improved thermal properties.
The ability to reduce transmission of infrared radiation, and specifically near infrared radiation, can be a particularly desirable characteristic of multiple layer glazing panels, and particularly for safety glass that is used in automotive and architectural applications. Reducing the transmission of infrared radiation can result in the reduction of heat generated by such radiation within an enclosed space.
Many examples exist in the art of compositions and methods to reduce infrared radiation transmission through multiple layer glazing panels. Included among these is the use of agents that selectively absorb radiation in the infrared region. One effective, known agent is lanthanum hexaboride (LaB6). Lanthanum hexaboride, while an excellent selective absorber of near infrared radiation, is subject to molecular degradation due to commonly encountered environmental conditions found in interlayers, which compromises the infrared absorbing ability of the interlayers.
Further improved compositions and methods are needed to enhance the characteristics of multiple layer glazing panels comprising infrared absorbing agents, and, specifically, multiple layer glazing panels comprising lanthanum hexaboride, so as to impart stability without detrimentally affecting optical qualities.